Poly(1,4-cyclohexenedimethylene terephthalate) [PCT] and copolyesters thereof with up to 40 mol % ethylene glycol are important polyesters in producing articles such as packaging materials, molding materials, etc. A problem which has been encountered has been producing the polymer at a fast reaction rate without causing an undesirable yellow color in the polymer, particularly where these polyesters are coextruded with polycarbonate to form alloys.
The present invention is based on a catalyst stabilizer system containing compounds of titanium and alkali or alkaline earth metal salts which permits fast production rates with little or no undesirable color.
U.S. Pat. No. 3,907,754 discloses a catalyst-inhibitor system containing titanium, manganese, cobalt, phosphorus for poly(ethylene terephthalate) which provides a fast reaction (production) rate and polymer with good color. This patent does not disclose antimony or an alkali metal salt as part of this catalyst combination, and does not address acetaldehyde generation. U.S. Pat. No. 3,962,189 discloses manganese, titanium, cobalt, phosphorus plus an alkali metal salt which is used to produce poly(ethylene terephthalate) with fast reaction rate, good color and an alkali metal salt in low concentration (2 to 32 ppm) to prevent a batho-chromic dye shift when the polyester is spun into fiber and dyed. This patent does not include antimony in the catalyst inhibitor system, and does not address acetaldehyde generation. U.S. Pat. No. 4,010,145 discloses a manganese, titanium, cobalt, phosphorus antimony catalyst inhibitor system for producing poly(ethylene terephthalate) at a fast rate with good color. There is no alkali metal salt disclosed in this patent and does not address acetaldehyde generation. U.S. Pat. No. 4,356,299 discloses a titanium, antimony, manganese, cobalt, and phosphorus catalyst system for producing poly(ethylene terephthalate) at fast rate with good color. This patent is for a reduced titanium concentration to provide good color and fast reaction rate, and does not address acetaldehyde generation. U.S. Pat. No. 4,357,461 discloses the use of an alkali metal salt of ethylenediamine-tetra acetic acid to reduce the acetaldehyde generation rate inherent in preparation and processing of poly(ethylene terephthalate) for packaging. However, this patent does not address the use of a titanium catalyzed polyester. U.S. Pat. No. 4,361,681 discloses the use of dicarboxylic acid anhydrides to reduce acetaldehyde in the preparation and processing of poly(ethylene terephthalate) for packaging and uses, namely bottles.